Antibacterial Activity and Biocompatibility of Nanoporous Titanium Doped with Silver Nanoparticles and Coated with N-Acetyl Cysteine

Abstract

Alkali-treated titanium with nanonetwork structure (TNS) is strongly osteogenic but not antibacterial in nature. In contrast, titanium doped with silver nanoparticles (Ag-NPs) possesses excellent and long-term antibacterial activity, but induces significant levels of intracellular reactive oxygen species that may cause cytotoxicity. We attempted to enhance the antibacterial activity of TNS by doping with Ag-NPs and prevent intracellular reactive oxygen species formation by coating with the antioxidant N-acetyl cysteine. Importantly, TNS doped with Ag-NPs and coated with N-acetyl cysteine has similar antibacterial activity against Staphylococcus aureus as TNS doped with only Ag-NPs, and inhibited bacterial attachment, proliferation, and biofilm formation by Actinomyces oris. However, TNS doped with Ag was significantly cytotoxic for rat bone marrow mesenchymal stem cells, whereas TNS doped with Ag and coated with N-acetyl cysteine supported cell viability and differentiation to a certain extent by suppressing overproduction of intracellular reactive oxygen species. Collectively, our results suggest that application of N-acetyl cysteine enhances the biocompatibility of TNS doped with Ag-NPs without compromising antibacterial activity, yielding a material with clinical potential.